A generally known dispenser having a container containing a liquid applies pressure to the liquid from behind to force the liquid out of the container and forms a pattern on a medium. The known dispenser is able to discharge a substance having a high viscosity and a substance having a low viscosity and to form patterns on a medium. However, in the known dispenser, it takes a long time for pressure to be propagated and hence the response of a liquid discharge operation to the pressure is not quick enough. Since the size of lines and dots is dependent on the outside diameter of a nozzle, the known dispenser is not suitable for minute patterning.
Another known method applies pressure to a liquid from behind the liquid and vibrates a portion of a dispenser around an outlet to form a liquid drop and attaches the liquid ball to a medium. This method, however, is unable to discharge highly viscous substance.
A pattern forming method that forms a pattern on a medium by discharging an ink from an orifice is known as an ink-jet patterning technique. The ink-jet patterning technique is exercised by a method that produces a bubble by heating a portion of a nozzle to force the ink out of the nozzle by the bubble, and a method that vibrates a piezoelectric ceramic element to force an ink out of a nozzle by a pressure generated by the vibration of the piezoelectric ceramic element. Each of these methods uses a very low force for forcing the ink out of the nozzle and is unable to discharge a highly viscous substance. The size of ink drops discharged from the orifice by the ink-jet patterning method is several times the diameter of the orifice.
This problem will be explained with reference to FIG. 9. Referring to FIG. 9, a highly viscous substance 2 is extruded through an opening formed in the tip of a nozzle 1 by electrostatic attraction or electromechanical pressure. A string 3 of the extruded highly viscous substance 2 of a predetermined length is cut off the tip of the nozzle 1. Then, the string 3 of the extruded highly viscous substance 2 becomes a spherical drop 4 by its own surface tension, and the spherical drop 4 adheres to a medium 5 in a dot. Therefore, the dot inevitably has a size as large as five to six times the diameter of the orifice of the nozzle 1.
The diameter of the orifice must be reduced to form a smaller drop. When it is required to discharge an ink containing large particles, the orifice of a small diameter is clogged, offset is abraded by the particles and the life of the discharge device is shortened.
An ink-jet device of an electrostatic attraction type also is unable to discharge a highly viscous substance.